1. Field of the Invention
The present invention is directed to avionic racking trays. More particularly, the present invention is directed to avionic racking trays of lightweight construction.
2. Brief Description of the Prior Art
Avionic racking trays have been known in the art for a long time. More particularly, in accordance with the usual practice in the aircraft building industry, each piece of electronic equipment used in aircraft is contained in a separate container ("black box") which is supported by an individual tray. The trays are, in turn, mounted substantially at their respective front and back ends on cross beams provided in the aircraft. The trays are usually made in standard ATR (aircraft tray racking) widths to accommodate various sizes of instruments.
The trays are usually mounted above a plate attached to the cross beams, so that the plate and the bottom sections of the trays jointly form an air plenum. Air is usually continuously evacuated from the air plenum. The trays usually have a depressed central portion into which a separate metering plate, having one or more air metering holes, is mounted, surrounded by a gasket.
The usual avionic racking trays include vertical side rails disposed at the lateral edges of a substantially horizontally disposed base plate of the tray. Still in accordance with standard practice in the art, a back plate is mounted with fasteners (such as bolts and nuts) between the side rails. The back plate has one or more openings or cut-out portions into which electrical connectors are mounted. Female receptacles of these connectors receive a plurality (usually a multitude) of male electrical connector pins which extend outwardly from the electronic equipment.
The safety of aircraft and its passengers often depends on the safe and reliable operation of various electronic equipment. To ensure such reliability the following aspects of the avionic racking trays and of the associated hardware were particularly recognized in the prior art.
The back plate must be disposed precisely at a right angle relative to the base plate of the tray in order to enable the male pins of the electronic equipment to engage matching female receptacles in the electric connector mounted to the base plate. Attaching the back plate to the side rails by ordinary nuts and bolts, however, does not provide sufficient precision for this purpose. As is described in detail in U.S. Pat. No. 3,710,476 this problem is solved in the prior art by providing jig pins in the interior sides of the side rails. The back plate is then provided with holes to register with the jig pins to provide a self-aligning assembly, which is fastened together by bolts and nuts, or other like fastener means.
Accurate mounting of the container for the electronic equipment (black box) into the tray for proper alignment of the male pins with the female receptacles is also important. At the same time it is highly desirable to establish sealing contact between the black box and the rubber or like gasket which holds the air metering plate in the tray. When these two related requirements are met, as in the structures described in U.S. Pat. No. 3,771,023, then air flows through an opening in the black box, through the metering hole in the metering plate, into the air plenum, and usually adequately cools the electronic equipment.
Still another important requirement recognized in the prior art relates to the manner the electronic equipment is inserted and removed from the tray. To maintain the multitude of male connector pins at all times substantially perfectly in alignment with the multitude of matching female connector receptacles, the prior art has devised an extractor and hold-down spindle which is described in U.S. Pat. No. 3,640,141.
A hitherto unsolved problem of avionic racking trays relates to weight. Up to the present invention, standard avionic trays have been made from 0.063" thick sheets of aircraft quality aluminum alloy, usually 6061-T6 (or equivalent) aluminum alloy. Those skilled in aluminum alloy metallurgy readily recognize that 6061 is a designation for the alloy which denotes the composition of the alloy, and that T6 is a designation which denotes a particular type of standard heat treatment given to the alloy.
Even though aluminum alloy 6061-T6 is structurally strong, it has been generally accepted in the art that the tray must be made of at least approximately 0.063" thick sheets. In fact, the ATR standard which has evolved in the aircraft industry is, by-and-large, based on the accepted fact that wall thickness of the standard trays is approximately 0.063". Nevertheless, reduction in weight of equipment incorporated into aircraft is always highly desirable. Therefore, there is a significant advantage to be gained in the art by reducing the weight of standard avionic trays. The present invention accomplishes this weight reduction without adversely affecting the structural strength or other advantageous properties of prior art avionic trays.